1. Technical field of the Invention
The present invention relates to an apparatus and a method for detecting an abnormality of a generator for vehicles.
2. Related Art
Conventionally, apparatuses are known which detect an abnormality of an alternator for vehicles. In one of these apparatuses, ripples are detected in the output voltage of a rectifier of an alternator. Then, the presence or absence of an abnormality of the alternator is determined based on the number of the ripples. Such an apparatus is disclosed, for example, in Japanese Patent Laid-open Publication No. 2003-61260.
However, the magnitude of the ripples varies in response to the output current and revolution speed of the alternator and the condition of a battery. Therefore, in the apparatus disclosed in Japanese Patent Laid-open Publication No. 2003-61260, there is a problem that it is difficult to accurately determine the presence or absence of an abnormality of the alternator based on the number of the ripples only. In addition, electric loads which are repeatedly and periodically connected and disconnected cause variations of the output voltage of the alternator. Consequently, the measurement error of the number of the ripples becomes large, thereby making it difficult to accurately determine the presence or absence of an abnormality of the alternator.